The invention relates to the field of automated welding, and more particularly, to an automated, gas metal arc welding apparatus for externally welding abutting sections of pipe.
Pipelines such as those used for the conveyance of oil or water are constructed by welding sections of pipe together. Often, the welding activities will be carried out by automated welding systems at the installation site of the pipeline. In some instances, automated welding systems capable of being moved along the pipeline right-of-way may be used.
Such mobile automated welding systems may comprise a welding carriage and a welding assembly, which includes a torch suitable for Gas Metal Arc Welding (GMAW). The welding carriage is adapted to carry the welding assembly around an annular track or guide mounted externally about one of the pipe sections. Typically, the welding carriage will have a motor for driving the carriage on the guide.
In the field, a variety of welding situations may present themselves. For example, the pipe sections to be welded may have large-angled bevels resulting in broad weld grooves. Conversely, other pipes having deep, thick sections will require that the weld be performed along a narrow weld seam. A flexible welding system is sought that is adaptable to such diverse conditions such that the welding operation can be effected with a single, mobile, apparatus. In addition, the welding system should be flexible enough to enable a substantially constant heat input to the weld.
In an aspect of the invention there is an apparatus for welding abutting pipe sections along a weld seam, the apparatus comprising: a motorized main carriage for travelling circumferentially about one of the pipe sections to be welded; a welding torch connected to the main carriage, the welding torch being movable relative to the main carriage; a first motorized transport mechanism connected to the main carriage for vertically displacing the welding torch relative to the weld seam; and a second motorized transport mechanism connected to the main carriage for pivotally moving the welding torch transversely of the weld seam.
In an additional feature of the invention the apparatus includes a controller for actuating the second transport mechanism so as to pivotally oscillate the welding torch transverse of the weld seam. In yet another additional feature, the controller actuates the first and the second transport mechanisms simultaneously so as to change the vertical position of a pivoting point of the torch in accordance with a pre-determined trajectory. In still another additional feature, the controller receives feedback as to a welding current, a welding voltage and actuates the first transport mechanism so as to effect a predetermined minimum heat input into the weld seam. In a further additional feature, the controller prioritizes the function of effecting said pre-determined minimum heat input over the function of following said pre-determined trajectory for the pivoting point of the torch.
In another additional feature, the apparatus further comprises a third motorized transport mechanism connected to the main carriage for linearly translating the welding torch transversely of the weld seam. In yet another additional feature, the apparatus includes a controller for activating the third transport mechanism so as to linearly oscillate the welding torch transverse of the weld seam. In still another additional feature, the controller is operable to actuate the first, the second and the third transport mechanisms simultaneously in order to effect a pre-determined trajectory and angular orientation of the torch relative to one of the vertical or transverse directions.
In another aspect of the invention, there is an apparatus for welding abutting pipe sections along a weld seam, the apparatus comprising: a motorized main carriage for travelling circumferentially about one of the pipe sections to be welded; a welding torch connected to the main carriage; the torch being movable relative to the main carriage; a first motorized transport mechanism connected to the main carriage for linearly translating the torch transversely of the weld seam; and a second motorized transport mechanism connected to the main carriage for pivotally moving the torch transversely of the weld seam.
In an additional feature of the invention, the apparatus includes a controller for actuating the second transport mechanism so as to oscillate the torch about a pivot point, transverse of the weld seam; and for actuating the first transport mechanism so as to linearly translate the pivot point transverse of the weld seam. In yet another additional feature, the first transport mechanism includes: a carriage connected to the welding torch, a motor for providing a driving force to effect linear translation of the welding torch; and a frame for supporting the motor. The frame is fixed to the main carriage. The carriage is slidably mounted to the frame and translatable relative to the main carriage in a direction transverse of the weld seam. In still another additional feature, the carriage has guide means fixed thereto. The guide means are slidably mounted to the frame. In a further additional feature the first transport assembly includes driving means interconnecting the motor and the carriage. In yet another additional feature the driving means include: a cog rotatably mounted to the motor for transmitting the driving force of the motor; a cog pulley rotatably connected to the cog and mounted to extend through the frame, the cog pulley including a threaded shaft rotatable about the frame; and a nut fixed to the carriage for threadingly engaging the shaft. The cog pulley is adapted to receive the driving force of the motor and to rotate the shaft. The nut is adapted is to travel along the shaft when the motor is actuated to thereby urge the carriage to translate transversely of the weld seam.
In another additional feature, the second transport assembly includes: a frame connected to the main carriage; a mount for carrying the welding torch; a motor for providing a driving force to effect pivotal motion of the welding torch, the motor being fixed to the frame; an eccentric cam connected to the motor; and a cam follower disposed intermediate the cam and the mount and pivotally attached to the frame. The cam follower is adapted to receive the driving force from the motor such that when the motor is actuated the cam follower is urged to rotate about the frame thereby causing the welding head to move pivotally in a direction transverse of the weld seam.
In yet another additional feature the second transport assembly includes: a frame connected to the main carriage; a mount for carrying the welding torch; a motor for providing a driving force to effect pivotal motion of the welding torch, the motor being fixed to the frame; an eccentric cam connected to the motor; and a cam follower disposed intermediate the cam and the mount and pivotally attached to the frame. The cam follower is adapted to receive the driving force from the motor such that when the motor is actuated the cam follower is urged to rotate about the frame thereby causing the welding head to move pivotally in a direction transverse of the weld seam.
In still another additional feature the second transport mechanism includes: a frame connected to the main carriage; a mount for carrying the welding torch; a motor for providing a driving force to effect pivotal motion of the welding torch, the motor being fixed to the frame; and a gear train connected to the motor. The mount is pivotally attached to the frame. The gear train is adapted to transmit the driving force from the motor to the mount to cause the welding head to move pivotally transverse of the weld seam.
In a yet another additional feature, the apparatus further comprises a third motorized transport mechanism connected to the main carriage for vertically displacing the welding torch relative to the weld seam. In a further additional feature, the controller is operative to actuate the first, second and third transport mechanisms simultaneously in order to effect a pre-determined trajectory and angular orientation of the torch relative to one the vertical or transverse directions. In still another additional feature the controller receives feedback as to a welding current and welding voltage and actuates the third transport mechanism so as to effect a pre-determined minimum heat input into the weld seam. In yet another additional feature the controller prioritizes the function of effecting said pre-determined minimum heat input over the function of following said predetermined trajectory for the pivoting point of the torch. In still another additional feature the third transport mechanism includes: a carriage connected to the welding torch, a motor for providing the driving force to effect the vertical displacement of the welding torch, and a frame for supporting the motor, the frame being connected to the main carriage. The carriage is slidably mounted to the frame and vertically translatable relative to the main carriage in a direction perpendicular to the pipe sections to be welded. In yet another additional feature the carriage has guide means fixed thereto, the guide means being slidably mounted to the frame. In still another additional feature, the third transport assembly includes driving means interconnecting the motor and the carriage. In a further additional feature, the driving means include: a cog rotatably mounted to the motor for transmitting the driving force of the motor; and a cog pulley rotatably connected to the cog and mounted to extend through the frame. The cog pulley includes a threaded shaft rotatable about the frame. The carriage has a threaded bore. The bore is adapted to receive the threaded shaft. The co pulley is adapted to receive the driving force of the motor and to rotate the shaft within the bore. The carriage is adapted to travel vertically along the shaft when the motor is actuated.
In another additional feature, the first transport mechanism has a motor-driven carriage that is translatable relative to the main carriage in a direction transverse of the weld seam. The frame of the third transport assembly is fixed to the carriage of the first transport assembly. In yet another additional feature, the second transport assembly has a frame and a mount connected thereto to support the welding torch. The frame of the second transport assembly is pivotally connected to the carriage of the third transport assembly.
In another additional feature, the frame of the third transport assembly is fixed to the main carriage; and the first transport mechanism has a motor-driven carriage that is translatable relative to the main carriage in a direction transverse of the weld seam. The carriage of the first transport assembly is fixed to the frame of the third transport assembly. In still another additional feature, the second transport assembly has a frame and a mount connected thereto to support the welding torch. The frame of the second transport assembly is pivotally connected to the carriage of the first transport assembly.
In yet another additional feature of the invention, the apparatus further comprises a retracting mechanism for rotating the welding torch away from the weld seam. The retracting mechanism includes a clamp for securing the welding head in position.